scholarly journals Orbital Asian summer monsoon dynamics revealed using an isotope-enabled global climate model

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Thibaut Caley ◽  
Didier M. Roche ◽  
Hans Renssen
Keyword(s):  
Summer Monsoon ◽  
Climate Model ◽  
Asian Summer Monsoon ◽  
Global Climate ◽  
Global Climate Model ◽  
Asian Summer ◽  
Monsoon Dynamics

The forced response of Asian Summer Monsoon precipitation during the past 1500 years

2020 ◽  
Author(s):  
Zhiyuan Wang ◽  
Jianglin Wang ◽  
Jia Jia ◽  
Jian Liu
Keyword(s):  
Summer Monsoon ◽  
Climate Model ◽  
Asian Summer Monsoon ◽  
Global Climate ◽  
Volcanic Eruptions ◽  
Tropical Pacific ◽  
Forced Response ◽  
Solar Irradiation ◽  
The Past ◽  
Asian Summer

<p>Asian summer monsoon (ASM) is one of the critical elements of the global climate system, and strongly affects food production and security of most people over Asia. However, the characteristics and the forcing drivers of the ASM system at decadal to centennial time scales remain unclear. To address these issues, we report four 1500-yr long climate model simulations based on the Community Earth System Model (CESM), including full-forced run (ALLR), control run (CTRL), natural run (NAT), and anthropogenic run (ANTH). After evaluating the performances of the CESM in simulating ASM precipitation, a 10-100 bandpass filter is applied to obtain the decadal-centennial signals in ASM precipitation. The main conclusions are (1) the variation of ASM intensity shows significant decadal to centennial periodicities in the ALLR, such as ~15, ~25, ~40, and ~70 years. (2) the major spatial-temporal ASM precipitation distributions in the ALLR show an external forced mode and climate internal variability mode, respectively. (3) The leading forced mode of ASM precipitation is mainly affected by natural forcing over the past 1500 years and characterizes a meridional spatial 'tripole' mode. In the NAT (solar irradiation and volcanic eruptions), the substantial warming (cooling) over the western tropical Pacific enhances (or reduces) the SST gradient change in the tropical Pacific, and modifying the ASM rainfall distribution. Our findings contribute to better understanding of the ASM in the past, and provide implications for future projections of the ASM under global warming.</p>

scholarly journals Transport of Asian surface pollutants to the global stratosphere from the Tibetan Plateau region during the Asian summer monsoon

2020 ◽  
Vol 7 (3) ◽  
pp. 516-533 ◽  
Author(s):  
Jianchun Bian ◽  
Dan Li ◽  
Zhixuan Bai ◽  
Qian Li ◽  
Daren Lyu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Global Climate ◽  
Pollutant Emissions ◽  
The Tibetan Plateau ◽  
Plateau Region ◽  
Radiative Processes ◽  
Asian Summer ◽  
The Impact

Abstract Due to its surrounding strong and deep Asian summer monsoon (ASM) circulation and active surface pollutant emissions, surface pollutants are transported to the stratosphere from the Tibetan Plateau region, which may have critical impacts on global climate through chemical, microphysical and radiative processes. This article reviews major recent advances in research regarding troposphere–stratosphere transport from the region of the Tibetan Plateau. Since the discovery of the total ozone valley over the Tibetan Plateau in summer from satellite observations in the early 1990s, new satellite-borne instruments have become operational and have provided significant new information on atmospheric composition. In addition, in situ measurements and model simulations are used to investigate deep convection and the ASM anticyclone, surface sources and pathways, atmospheric chemical transformations and the impact on global climate. Also challenges are discussed for further understanding critical questions on microphysics and microchemistry in clouds during the pathway to the global stratosphere over the Tibetan Plateau.

Investigating the sensitivity of the onset and withdrawal of the south Asian summer monsoon system to changes in anthropogenic emissions using a climate model

2020 ◽  
Author(s):  
Shiwansha Mishra ◽  
Dilip Ganguly ◽  
Puneet Sharma
Keyword(s):  
South Asian ◽  
Summer Monsoon ◽  
Climate Model ◽  
Asian Summer Monsoon ◽  
Anthropogenic Emissions ◽  
South Asian Summer Monsoon ◽  
The South ◽  
Monsoon System ◽  
Asian Summer ◽  
The Impact

<p>While the monsoon onset is recognized as a rapid, substantial, and sustained increase in rainfall over large parts of south Asia, the withdrawal marks the return to dry conditions. Normally, the south Asian summer monsoon onset occurs around 1<sup>st</sup> June over extreme south of peninsular India, which gradually advances to extreme northwest of India by around 15<sup>th</sup> July. The withdrawal starts from northwest India from around 1st September and from extreme south peninsular India by around 30th September. The determinations of the onset and withdrawal dates of monsoon have great economic significance for this region as they influence many agriculture and water resource management decisions in one of the most highly populated regions of the world. Several studies involving global model simulations have shown that changing aerosol emissions could result in significant changes in the seasonal mean precipitation distribution over India. A few studies also show that presence of absorbing aerosols in the foothills of Himalayas and over the Tibetan plateau could increase the moisture convergence over India thereby causing an advancement and intensification of the monsoon precipitation. However, most of the previous studies, which investigated the impact of anthropogenic emissions on the monsoon, are limited to understanding the impact of various emission changes on the seasonal mean monsoon characteristics. In the present study, we try to understand the sensitivity of the onset and withdrawal period of the south Asian summer monsoon system to changes in anthropogenic emissions using a climate model (CESM1.2). We diagnose the onset and withdrawal of the south Asian monsoon by analyzing the variability in vertically integrated moisture transport (VIMT) over the south Asian region and following the definition of hydrologic onset and withdrawal index (HOWI) defined by Fasullo et al. (2002). We examined the effect of changing emissions anthropogenic aerosol, greenhouse gases and both on the onset and withdrawal of the south Asian summer monsoon system. Our preliminary results suggest that increases in the emissions of aerosols and greenhouse gases from anthropogenic sources from pre-industrial to present day could possibly result in significant delay in the onset and advancement in withdrawal of the south Asian summer monsoon system thereby shortening the length of the monsoon season. More results with greater detail will be presented.</p>

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